1. Field of the Invention
The invention relates to a method and apparatus for determining physiological parameters indicative of lung condition, which parameters are independent of air flow rates based on nitrogen monoxide content in exhalation, which content is dependent on air flow rates.
2. Description of the Prior Art
It is known that nitric oxide (NO) is produced in the lung and appears in the exhaled breath. The exhaled concentration is elevated in important inflammatory diseases such as asthma. A significant fraction of exhaled NO which is unique among endogenous gases comes from the airways. A single breath technique has been invented by one of the inventors and is the subject of a copending application in a prior application, which technique required inhalation to total lung capacity followed by a breath hold of up to 20 seconds followed by an exhalation with a decreasing flow rate which lasted approximately 15 seconds. Thus approximately 35 seconds was required to complete the maneuver. This duration is not possible for subjects who cannot follow directions (i.e., small children or subjects who are unconscious) or who have compromised lung function.